This jacket has wide shoulder and wide armholes so you'll get shoulder dropped silhouette when you wear it. If you have TCB 50's Jacket or S40's Jacket, we recommend the same size.
If you don't have any other TCB jacket, we recommend you measure the shoulder width and sleeve length of your favorite jacket and choose a size based on the shoulder & sleeve added number.
Because the cut itself is a bit loose and relaxed, we'd say a relaxed fitting size would look better than a snug fitting size.